Field of Invention
This invention relates to a semiconductor process, and particularly relates to a contact process for a semiconductor device and a contact structure formed thereby.
Description of Related Art
A doped region of a semiconductor device that is required to be electrically connected to other element is usually connected to a contact plug first. In order to prevent ion impurity from entering the contact plug and also avoid a short circuit with a conductive part other than the target doped region, such as the gate in a MOS structure of the semiconductor device, an insulating liner layer is often formed on the sidewall of the contact hole before the conductive material of the contact plug is filled in the contact hole.
The insulating liner on the sidewall of the contact hole is usually formed by depositing a blanket layer and anisotropically etching the same to remove the portion of the insulating liner layer at the bottom of the contact hole. In order to well remove the portion to ensure a good electrical connection, over-etching is usually performed. However, it is possible that the metal silicide layer on the doped region for lowering the contact resistance is etched through in the over-etching process so that the contact resistance is increased.